1. Field of the Invention
The present invention relates to a thin-film transistor, a fabrication method thereof, and an image display device.
2. Background Art
With rapid advances in information technology, sending and receiving of information through devices such as laptop personal computers and portable information terminals have not been more extensive. It is commonly accepted that the ubiquitous society, where people can exchange information at any place, is the trend of the future. Lighter and thinner information terminals are thus desired of such an information society.
Currently, the mainstream semiconductor materials are silicon (Si) based. However, transistors that use oxide semiconductors (oxide transistors) have been actively studied from various perspectives, including flexibility, lightness, cost, and performance. Vacuum deposition such as sputtering is typically used for oxide semiconductors.
In recent years, there have been reports of oxide semiconductors formed by coating. This has widened the range of potential applications such as increasing the product area, use of the printing method, and use of plastic substrates.
The applicable areas include a wide range of fields, including thin and light-weight flexible displays, and, potentially, RFID (Radio Frequency Identification) tags and sensors. Indeed, studies of coating-type oxide transistors are essential for the advent of the ubiquitous society.
For these and other reasons, studies of oxide semiconductors that employ coating have attracted interest.
Spin coating, dipping, and inkjet methods are among the methods of forming a semiconductor layer from a solution. Spin coating and dipping can be used to fabricate a transistor array that includes a plurality of transistors. A problem of such transistor arrays, however, is that a current easily flows in the semiconductor layer between the transistor devices or between the transistors and the pixel electrode, and increases the OFF-state current (leak current) and lowers the ON/OFF ratio.
As a countermeasure, JP-A-2005-210086 realizes isolation of transistor devices with a semiconductor layer formed at the desired place by using an inkjet method. JP-A-2004-80026 realizes isolation of transistor devices by injecting a semiconductor solution into a channel portion between a source electrode and a drain electrode.
However, injecting a semiconductor solution into a channel portion as in JP-A-2004-80026 requires a partition wall, and the common transistor fabrication additionally requires deposition of the partition wall material and a patterning process.